1. Field of the Invention
The invention relates to the paper making process, and in particular, to removing the curl from a strip of sheet material wound upon a roll. In particular, the present invention relates to devices for removing the curl from paper being removed from a storage or supply roll for cutting into flat sheets.
2. Description of the Related Art
It is well known in the art that sheet material, such as a web or sheet of paper, paperboard, or paper laminates, develops a curvature or curl when wound upon a storage roll at the end of the manufacturing process. When a storage roll is removed from storage to supply paper for further processing, the storage roll then becomes the supply roll. As paper is drawn from the storage roll in a continuous sheet to be cut into individual sheets or made into other products, the curl must be removed from the paper as it is removed from the supply roll.
Many devices are known in the art for removing curl from paper. Some devices include a metal bar aligned parallel to the axis of rotation of the supply roll over which the paper sheet is pulled at an angle to the direction from which the paper sheet is pulled from the supply roll. Such bars are referred to in the art as "curl bars".
Exemplary of the many devices for removing curl from sheet material on a storage or supply roll are the following U.S. Patents:
U.S. Pat. No. 4,788,846 discloses a process for the correction of curls of flexible metal clad laminate and for the improvement of its dimensional stability, the laminate having a thin aromatic polyimide film formed on a long metal foil, the laminate being caused to slide under tension, along its length, on curved surfaces of four bars arranged at specific positions, so that its curls are corrected and its dimensional stability is improved. In column 11, lines 3 through 11, the material of the bars is disclosed as being high-rigidity material such as glass, ceramic, metal or synthetic resin, most preferably, a strong ceramic such as zirconia ceramic, and their cross-sections (namely, cross-sections perendicular to the lengths of the bars) may be of any desired shape such as a rectangle, square or circle having a curve portion as shown in FIG. 7 or FIG. 8.
U.S. Pat. No. 4,360,356 discloses a decurler apparatus for removing curl from a continuous moving web. The apparatus includes cylindrical members between which the web travels. The engagement members are pivotally movable so that either surface of the web can be engaged by one of the engagement members with any desired degree of pressure for removing the curl in the continuous web during travel thereof. If the curl is upwardly, the engagement members are pivoted to engage the opposite surface of the web. The degree of pressure applied for decurl action can be adjusted by adjusting the angle of the engagement members with respect to the line of travel of the continuous web. The apparatus also includes brush members engageable with the web to control the tensional forces upon the web as the web engages one or both of the engagement members.
U.S. Pat. No. 3,971,696 discloses a paper web decurling apparatus including a freely rotatable relatively large diameter support roll and a freely rotatable small diameter decurling roller disposed parallel to the support roll for pressure engagement with a paper web thereon. Selectively operable devices are provided for adjustably varying the pressure of the decurling roller against the paper web and support roll and selectively operable devices are provided to rotationally position the decurling roller to engage the paper web on the support roll at any desired location circumferentially of the support roll.
U.S. Pat. No. 3,962,957 discloses a curling device for webs of paper or the like which are used for the making of adhesive-coated uniting bands in filter cigarette making machines including a curling bar having a sharp edge which extends transversely of and flexes the running web to eliminate localized stresses in the material of the web and/or to equalize the length of lengthwise extending portions of the web. The bar is pivotable or otherwise movable in its support (e.g., it can be mounted for pivotal movement about an axis which is normal to the edge) so that the bar can change its angular position in reponse to unequal distribution of web pressure lengthwise of the edge. Such mounting of the bar reduces the likelihood of breaking the web when the length of the one and/or other marginal portion of the web exceeds the length of the median portion. In Column 9, lines 4-7, the curling device is disclosed as preferably consisting of steel or another suitable metallic material; however, certain types of synthetic plastic materials can be used instead of or as coatings for metallic curling devices.
U.S. Pat. No. 3,649,447 discloses an apparatus for decurling a paper web as it is being fed from its supply roll including a frame having a pivotable decurl member mounted on a pivotable linkage and positioned in a web path and a rubber-covered roll operatively connected to the linkage and engaging the supply roll surface such that the angle the decurl member makes with the web path is caused to change to vary the degree of decurl in response to the changes in the roll diameter. The decurl member comprises a generally circular member subtended by a chordal portion forming a decurling edge thereon.
U.S. Pat. No. 2,737,089 discloses an apparatus for decurling a web after leaving its supply roll and prior to other operations thereon, the combination of two spaced sets of feed rolls, continuously engaging the web, a decurling member disposed between the sets of rolls against which the web is fed as it passes from one set of rolls to the other, positively and continuously acting drive device for each set of rolls, the set of rolls beyond the decurling member acting to feed the web at a higher speed than that of the other set of rolls to produce a tension in the web as it passes over the decurling member, a device for continuously exerting a positive nipping pressure on the web between the rolls of each set, a device for varying the nipping pressure between one set of rolls as compared to the other to vary the effective tension of the web as it is carried over the decurling member, other feed rolls spaced from the sets of feed rolls and operating at a speed permitting the formation of a free loop in the web between the other feed rolls and the spaced sets of feed rolls, and a device controlled by the loop for reducing the speed of the spaced sets of feed rolls relative to the other feed rolls to limit the size of the loop in the web.
U.S. Pat. No. 2,339,070 discloses a sheet decurling apparatus and a guide member engaging opposite sides of a traveling sheet, arranged to bend the sheet across the decurling member, and an adjusting construction for varying the spacing of the decurling member and the guide member in the direction of sheet travel.
U.S. Pat. No. 1,114,468 discloses a method for treating paper for spiral mouthpieces of cigarettes which is a process for rendering elastic the paper out of which the spiral mouthpieces for cigarettes are made, including drawing the entire paper strips under continuous tension over a sharp edge, the entire paper strips being bent while being drawn over the sharp edge.